1. Field of the Invention
This invention relates to the field of polymer treatment apparatuses and methods for processing polymer waste wherein the waste is processed in a form suitable for recycling.
2. Description of the Prior Art
According to known procedures continuous polymerization lines are operated to produce polymer products. One such product is pellets of polymer for further use, such as remelting to produce melt-spun thermoplastic filaments, for example, of nylon or polyester. During routine maintenance of such pelletizing equipment or during system failures the stream of molten polymer from the continuous polymerization line cannot be stopped and must be diverted to waste Normal procedure for machines with a capacity of only one thousand to three thousand pounds per hour is to extrude the polymer directly onto the floor next to the pelletizer or into a buggy during the limited time the pelletizer is not operational. The waste, or xe2x80x9cplopxe2x80x9d, collected in this manner is manually handled to prepare it for recycle as a second quality polymer.
An alternative to placing plop on the floor or into a buggy is disclosed in U.S. Pat. No. 5,496,508 (Hettinga et al). In this patent the purged polymer is directed into a hopper and between two rollers, which cool and compress the purge to a continuous strip thickness suitable for subsequent processing. The strip is collected in a hollow steel container. The strip may be corrugated on one side or split into a plurality of strips. Other alternatives are disclosed by Japanese Patents JO 72 27874 and JO 81 55957 where in both separate cases the waste polymer is separated into discrete volumes and placed into individual containers that are part of a conveying system. In the former patent the polymer stream is never interrupted and is only temporarily diverted as the containers are switched. In the latter patent the polymer is collected between a fixed plate and a moveable plate that opens and closes periodically to discharge a discrete volume of polymer and cut it into a block that falls into a conveyed bucket containing a quench fluid. There is no indication that these alternatives can handle more than one thousand to three thousand pounds per hour of molten polymer.
When the capacity of the continuous polymerization pelletizing line is greater than three thousand pounds (1360 Kg) per hour (up to twelve thousand pounds (5440 Kg) per hour) it becomes unwieldy, labor intensive, and dangerous to handle the large volume of hot polymer which approaches two hundred pounds(1.5 Kg) per minute or 3.3 pounds per second. Such large quantities of molten polymer collected in one mass also present a significant fire hazard in the area. For nylon polymer with a specific gravity of 1.2, this is about 2.7 cubic feet (0.08 cubic meters) per minute of polymer at about three hundred (300xc2x0 C.) degrees Centigrade. If this quantity of nylon polymer is exiting out of a three-inch (7.62 cm) diameter pipe, the velocity of polymer to be handled approaches eleven inches (27.9 cm) per second. There is a need for a system to safely and economically handle large flow rates of molten polymer waste in a way that makes it easy to recycle.
The invention is a method and apparatus to process a diverted molten polymer waste stream by directing the polymer stream to one of at least two passages, separating the molten polymer into individual pieces or segments while containing the polymer and discharging the polymer from a containment exit, cooling each segment with a quench fluid to form a solid or semi-solid polymer, and transporting the solidified segments away from the containment exit and into a container using the quench fluid. One preferred apparatus comprises a cross-section transition connector, a moveable block with two passages, a block oscillator, a cut-off plate, an open space above an inclined transporting device, a quench fluid jet, and a quench fluid transporting trough. The transporting trough is designed to provide adequate time and cooling for solidification of polymer segments and to transport the segments to a desired location laterally spaced from the containment exit. The cross-section transition connector changes the polymer cross-section from cylindrical to a flattened cylinder, which reduces the distance required to traverse and cut the polymer stream. Directing the polymer stream to one or the other or both of at least two passages provides a continuous path for the polymer stream so pressure does not build up in the polymer that may damage elements in the system, and so gravity draining is provided when the system shuts down. Other apparatuses show other means of accomplishing the directing of polymer using a conically shaped bloc that is rotatably moved. Movement of the block in some apparatuses may occur in either reciprocating rectilinear directions or in a rotational direction.